The present invention relates to a structure of a printer head for a dot printer, in particular, relates to such a printer head which is small in size and can operate with less power consumption.
FIG. 1 shows the principle of the dot matrix printing in a serial printer. A printer head 100 has seven needles for mosaic printing, and travels along a printing line in the direction of the arrow A. During the travelling, needles are selectively driven to hit a paper through an ink ribbon and a desired pattern "A", "B", "C" or "D" is printed. The selection of needles is controlled by the content of an integrated circuit (IC) memory. When the size of a character to be printed is 2.67 mm.times.2.05 mm, 7.times.5 number of dots are enough for printing a recognizable character.
The prior needle dot head for dot printing process is shown in the U.S. Pat. No. 3,896,918, in which an electromagnetic drive for the operation of printing needles of a mosaic printing head includes a pivotally mounted armature for each needle which are arranged along circular arc. The construction includes a common yoke for all of the electromagnets which comprises two concentric cups or walls forming a single unit with cylindrical cores arranged at equal intervals along a circular arc parallel to the genatrix of the cup and located between the individual yoke cups.
However, said prior printing head has the disadvantages that the power consumption for driving needles is large, the size of the apparatus is large, and the operational speed of the printer is rather slow. Those disadvantages come mainly from the fact that a needle is drived by an electromagnet, and all the printing power for striking a paper by a needle is provided by said electromagnet.